The present invention generally relates to internal combustion engines. More specifically, the invention relates to a device and arrangement which facilitates the manual rotation or "barring" of engine crankshaft-driven components during adjustment or repair.
In internal combustion engines, many components are synchronously actuated by the engine crankshaft, e.g., valves, fuel injectors, and other timed components. Thus, in the adjustment or repair of such engine components, the crankshaft is manually rotated or "barred over" to bring the selected parts to a desired position. Barring is done during valve lash adjustment, setting injector travel, and other repairs. Particularly on large diesel engines, barring has conventionally been accomplished by rotating an external accessory drive pulley driven by a crankshaft-mounted pulley. Each external pulley requires an external rotational shaft seal on the engine casing.
State-of-the-art engine design, however, avoids externally-exposed rotational shaft seals when possible, hence eliminating external pulleys which could be used for barring. For example, an engine developed by Cummins Engine Co. has no external accessory drive pulley and, in fact, has no external rotational shaft seals except at the crankshaft. Instead, this engine has a front gear casing which seals and encloses a series of crankshaft-driven drive gears. These enclosed gears operate rotational components including an air compressor. Of course, the elimination of expensive external rotational seals minimizes possible leakage points and intrusion of external debris. This can reduce wear and increase mileage between overhauls.
An engine without an accessory drive pulley, such as the engine described above, could possibly be barred over by directly rotating the exposed crankshaft nose. Unfortunately, the crank nose location is impractically difficult to access when the engine is mounted on a truck chassis. This is because the crank nose is located in a low position close to the truck frame. Also, the crankshaft nose is inconveniently far from a mechanic's common work position during barring--near the head of the engine where the valves and injectors are located. A barring location higher on the engine is desirable so that a mechanic can torque the barring tool while also having convenient access to components at the engine head.
Given the elimination of conventional barring points at external pulleys on modern engines, a need exists for a new device and arrangement to facilitate convenient engine barring.